What is it about?
This study explores the different forms of carbon found deep within the Earth's mantle. By analyzing rocks from mid-ocean ridges across the globe, researchers found that the carbon in these areas has varied isotopic signatures. The findings suggest that the Earth's mantle is more diverse in its carbon composition than previously thought which in turns suggest a variety of origins for this carbon.
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Why is it important?
What makes this work unique is its comprehensive dataset of carbon isotope measurements from rare un-degassed mid-ocean ridge rocks, revealing significant heterogeneity in the carbon isotopic signature of Earth’s upper mantle. Unlike previous assumptions that the bulk silicate Earth has a uniform carbon isotopic value, this study shows that the carbon isotopic signature of the upper mantle may be quite varied between mantle domains. This challenges existing models and suggests that ancient heterogeneities might still exist in the mantle. Our understanding of Earth's deep carbon cycle and carbon origin may need revising.
Perspectives
This research combined a unique collection of samples with an innovative analytical approach. The samples, consisting of undegassed lavas from mid-ocean ridges around the world, are exceptionally rare. Among the thousands of lava samples collected from these ridges, only a few have remained undegassed, preserving their original CO2 content and isotopic signature. Recently, we developed an analytical method to measure the isotopic signature of these glass samples using Secondary Ion Mass Spectrometry (SIMS). Our results paint a very different picture for carbon in the Earth's mantle, revealing significant heterogeneity where uniformity was expected. I am excited about the prospect of expanding this research to more locations to further refine this new picture.
Yves Moussallam
Columbia University
Read the Original
This page is a summary of: Enigmatic carbon isotopic variability in the oceanic upper mantle, Proceedings of the National Academy of Sciences, June 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2502886122.
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